1. Field of the Invention
The present invention relates to a signal processor utilizable, for example, in processing voice signals.
2. Description of the Prior Art
FIG. 25 is a block diagram of a conventional signal processing apparatus. In FIG. 25, a filter controller 1 distinguishes a voice component and a noise component in a signal input thereto, that is, controls a filtration factor of a bank of band-pass filters 2 (hereinafter referred to as a BPF bank) corresponding to the voice or noise component of the input signal. The BPF bank 2 is followed by an adder 3 which divides the input signal into frequency bands. The passband characteristic of the input signal is determined by a control signal from the filter controller 1.
The conventional signal processing apparatus of the above-described construction operates as follows.
When an input signal having the noise component superposed on the speech component is supplied to the filter controller 1, the filter controller 1 subsequently detects the noise component from the input signal in correspondence to each frequency band of the BPF bank 2, so that a filtration factor for not allowing the noise component to pass through the BPF bank 2 is supplied to the BPF bank 2.
The BPF bank 2 divides the input signal appropriately into frequency bands, and passes the input signal with the filtration factor set for every frequency band by the filter controller 1 to the adder 3. The adder 3 mixes and combines the divided signal so as to thereby obtain an output.
In the aforementioned manner, conventionally, the level of the input signal in the frequency band including the noise component is lowered, and as a result of this, an output signal having an attenuated noise component is obtained.
According to the aforementioned manner, however, some noise components still remain to be removed.
Moreover, according to the conventional method, the noise component is distinguished from the voice component simply in time sequence. The noise component and voice component in the signal are attenuated or amplified in its entirety, and therefore the S/N ratio is not particularly enhanced.